1. Field of the Invention
The present invention relates to a heater module of an apparatus for rapid thermal processing, and more particularly to a heater module of a rapid thermal processing apparatus comprising cooling means for lamps, and the like.
2. Description of the Prior Art
A representative example of an apparatus for thermal processing of wafers is an apparatus for rapid thermal processing (RTP). The rapid thermal processing apparatus is used to perform rapid thermal annealing, rapid thermal cleaning, rapid thermal chemical vapor deposition, rapid thermal oxidation, and rapid thermal nitridation processes.
In a case of the rapid thermal processing apparatus, it essentially requires accurate control of temperature, since the wafer temperature is elevated or lowered over a relatively wide range within a very short period of time. For this accurate control of temperature, first of all, it has to be essentially examined whether a heater module of the rapid thermal processing apparatus is designed to uniformly supply heat to wafers. The rapid thermal processing apparatus uses halogen lamps as a heating source. Such halogen lamps have various shapes and power sources. According to the shape of the halogen lamp, a heater reactor provided in the heater module may be variously changed in shape. The heater reactor serves to fix the tungsten halogen lamps and thus allow effective use of that heating source. For this, the heater reactor is used to install reflective plates at the side surface or rear surface of the respective lamps. According to the shape of these reflective plates, distribution of temperature may be considerably altered.
FIGS. 1a through 1c are schematic views, respectively, illustrating different embodiments of a heater module for a rapid thermal processing apparatus in accordance with the prior art.
Referring to FIG. 1a illustrating a first embodiment of a heater module according to the prior art, the heater module comprises a heater reactor 11 having a plurality of reflective plates 13, and a plurality of bulb type tungsten halogen lamps 12. The halogen lamps 12 are installed inside the heater reactor 11 in such a fashion that they form several concentric circles of different diameters while being spaced apart from one another. The respective reflective plates 13 are arranged to separate one concentric circle from another adjacent concentric circle. That is, all of light beams, emitted from the lamps 12 arranged along the same circumference of the concentric circles, are reflected by one reflective plate 13 associated therewith. Therefore, in this case, it is impossible to achieve accurate control of temperature since the temperatures of the lamps 12, positioned on the same circumference, are integrally controlled.
Referring to FIG. 1b illustrating a second embodiment of the heater module according to the prior art, the heater module comprises a plurality of bulb type lamps 22 arranged inside a heater reactor 21 to form several concentric circles of different diameters, in the same manner as the first embodiment shown in FIG. 1a. This second embodiment, however, is different from the first embodiment in that the heater reactor 21 has reflective plates 23 each having the same tubular shape as the bulb type lamps 22, and in that the lamps 22 are installed inside the heater reactor 21 in such a fashion that they correspond to respective reflective plates 23 in a one-on-one fashion, respectively, thereby being adapted to apply heat to a specific desired region. The heater module constructed as stated above has a disadvantage in that the radiation angle of the respective lamps 22 is too small, resulting in poor thermal efficiency. Therefore, the heater module of the second embodiment requires a greater amount of lamps when compared with the heater module shown in FIG. 1a. This results in increased complexity of a temperature control device and an increase in manufacturing costs of the system.
Referring to FIG. 1c illustrating a third embodiment of the heater module according to the prior art, the heater module comprises a heater reactor 31 having only one reflective plate 33, and a plurality of elongate stick type lamps 32. The stick type lamps 32 are installed inside the heater reactor 31 in such a fashion that they are positioned above a wafer in parallel to the wafer in order to improve a thermal efficiency of the lamps 32. The reflective plate 33 is adapted to reflect all of light beams emitted from all of the lamps 32. In this case, however, since the radiation angles of the light beams emitted from the respective lamps 32 are interfered and overlapped with one another, it is impossible to achieve accurate control of the temperature of a specific region.